Preparation and characterization of microencapsulated LDHs
with melamine‐formaldehyde resin and its flame retardant
application in epoxy resin
College of Materials Science and Technology,
Nanjing Forestry University, Nanjing 210037,
Hailan Lian, College of Materials Science and
Technology, Nanjing Forestry University,
Nanjing 210037, China.
Priority Academic Program Development of
Jiangsu Higher Education Institutions; Jiangsu
Province Science Foundation for Youths,
Grant/Award Number: BK20150876; Natural
Science Foundation of China, Grant/Award
Layered double hydroxides (LDHs) are emerging as a new and green high‐efficient
flame retardant. But LDHs aggregate seriously because of their hydrophilicity, which
affect deeply the mechanical and flame retardant properties of their composites.
For the first time in this paper, microencapsulated LDHs (MCLDHs) with melamine‐
formaldehyde (MF) resin were prepared by microencapsulation technology to
enhance their compatibility and dispersion within epoxy resin (EP). The mechanical
and flame retardant performances of EP/MCLDH composite were studied by compar-
ing with EP/LDH composite. Results showed that the water contact angle of
MCLDHs increased from 8.9° to 122.1°, which indicated good compatibility. The par-
ticle size of MCLDHs decreased sharply, and more than one‐third were up to submi-
cron scale, which can be conducive to dispersion. Moreover, the tensile strength and
elongation at break of EP/MCLDHs with different flame retardant contents were
higher than those of EP/LDHs. And the addition of MCLDHs increased the glass tran-
sition temperature (Tg) of EP/MCLDHs, which meant a strong interfacial interaction.
Besides, compared with EP/LDHs, the limiting oxygen index values of EP/MCLDHs
were higher, and its peak of heat release rate and total heat release decreased by
16.3% and 5.5% respectively. EP/MCLDHs achieved from V‐1toV‐0 rate with the
increasing content of MCLDHs from 20% to 30%, while LDHs/EP never passed tests.
In the process of heating, H
, and NH
released from MCLDHs formed gas-
eous phase, and the remaining dense char layers and oxides produced condensed
phase, which played an important role in inhibiting combustion.
epoxy resin, flame retardancy, layered double hydroxides, melamine‐formaldehyde resin,
Epoxy resin (EP), 1 of the most important thermosetting materials, has
been widely applied in the fields of protective coatings, structural
adhesives, composites, construction materials, and so forth because
of its excellent comprehensive properties of electrical insulation, low
shrinkage, outstanding mechanical stiffness, satisfactory adhesion,
and solvent resistance.
However, just as most of the polymer
materials, the inherent flammability of conventional EP restricts its
application in many areas where fire safety is paramount.
a great deal of attention has been paid to the development and appli-
cation of high‐performance flame retardant EP.
containing flame retardants prove effective and have been extensively
used to suppress their flammability, the flame retardant EP containing
bromine or chlorine can produce large amounts of toxic smoke and
corrosive substances during combustion, which is harmful to the
Received: 9 January 2018 Revised: 11 March 2018 Accepted: 21 March 2018
Polym Adv Technol. 2018;29:2147–2160. Copyright © 2018 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/pat 2147